BORON AND SILICON - EFFECTS ON GROWTH, PLASMA-LIPIDS, URINARY CYCLIC-AMP AND BONE AND BRAIN MINERAL-COMPOSITION OF MALE-RATS

Because boron resembles silicon in its chemical properties, an experim ent was performed to determine if excessive dietary boron would affect the response to silicon deprivation and, conversely, if silicon would influence the effects of an excessive intake of boron. Male weanling Sprague-Dawley rats were assigned to groups of six or 12 in a two-by-t wo factorially arranged experiment. Supplemented to a ground corn/case in diet containing 1.2 mug silicon and 3 mug boron per gram were silic on as sodium metasilicate at 0 or 50 mug/g and boron as orthoboric aci d at 0 or 500 mug/g diet. At nine weeks, animals fed high dietary boro n had significantly decreased final body weights, liver-weight-to-body -weight ratios, urinary cAMP concentrations, plasma triglyceride, chol esterol, glycine, valine, leucine, and lysine concentrations and skull copper, sodium, and manganese concentrations. High dietary boron also significantly increased brain-weight-to-body-weight ratios, magnesium concentrations of femur, brain, and plasma, zinc concentration of fem ur, and iron concentration of skull. The bone mineral findings suggest that excess dietary boron exerts subtle effects on bone composition. Dietary silicon affected blood urea nitrogen, hematocrit, hemoglobin, and the concentrations of plasma threonine and aspartic acid in animal s fed excess boron. Depression of the testes-weight-to-body-weight rat io of animals fed 500 mug boron per gram diet was most marked in anima ls not fed silicon. Although excessive dietary boron did not markedly enhance the response of rats to silicon deprivation, dietary silicon a ffected their response to high dietary boron. Thus, dietary silicon ap parently can influence boron toxicity.